The invention relates to a latch needle with the characteristics of the preamble of claim 1.
A latch needle for knitting machines is known from DE-AS 11 13 537, whose latch is pivotably seated in a latch slit and is in contact with a leaf spring arranged in the latch slit. The leaf spring is used to set defined pivot positions of the latch in the manner of detent positions.
The latch spring rests against the end of the latch located in the latch slit. If the latch is pivoted, the end of the latch rubs against the latch spring. This often leads to wear of the material of the latch and the leaf spring, wherein the leaf spring possibly slowly digs into the end of the latch. Because of this wear of the material, which can take place in an undefined, one-sided and spotty manner, the leaf spring possibly has a tendency to tilt, which has a negative effect on the ability of the latch needle to function.
As a rule, the latch slit forms a passage which is open toward the latch, as well as toward the side facing away from it, the needle back. However, the latch spring closes off this passage to a large extent. As a result, dust and fluff, which occur in particular in the course of processing hair yarn, cannot easily be removed from the latch slit. Instead, dirt tends to collect in the latch slit on top of the latch spring and in the end hampers the orderly functioning of the latch needle.
Based on this it is the object of the invention to produce a latch needle which as a whole is functionally more dependable.
This object is attained by means of the latch needle in accordance with claim 1.
The latch needle in accordance with the invention has a specially designed latch spring, which has at least two areas of different width along its longitudinal extension. For example, it is designed as a leaf spring of rectangular, oval or round cross section, wherein the cross section can be varied over the length of the latch spring, if required. The latch spring has a wider section, which is particularly provided for constituting a contact area for the latch. Wear occurring at the latch end and the leaf spring can be reduced because of the widened surface. Moreover, the leaf spring lies flat against the latch end, which counteracts tilting tendencies of the latch needle.
On the other hand the latch spring has at least one second section in which it is embodied to be narrower. A gap-like passage between the latch needle and the adjoining slit wall is formed because of this. Fluff and rubbed-off particles can leave the latch slit through this passage. Blockage of the latch slit is prevented to a large extent by this.
The capability of the latch needle can be improved because of the reduced wear, because of the prevention of one-sided and merely spotty removal of the material of the latch and the leaf spring, and therefore because of the avoidance of spring tilting or lateral spring deviations, and because of the prevention of fluff collections in the needle slit. This is valid especially during processing of heavy yarn for examples yarn which is hairy or otherwise dispose dust and wear off.
With a preferred embodiment, the ends of the latch needle are seated in spring receivers, or are received therein. The ends of the latch spring preferably have a width approximately corresponding to the latch slit. Because of this the latch spring is seated flat in the spring receivers, which counteracts a tendency of the latch spring to tilt. This can be of particular importance if, for achieving sufficient springiness, the cross section of the latch spring is laterally compressed in the area of reduced width, i.e. if in this area the latch spring has a height, measured parallel with the latch slit wall, which is as great or greater than its width.
The design of the latch spring in accordance with the invention with two sections having different width can be applied to embodiments wherein the latch spring is straight, i.e. elongated, as well as to embodiments wherein the latch spring has one or several bent places. In both cases the latch is preferably widened in the area of the latch seating device, so that it is seated with little play between the almost level latch slit walls. Because of this, the latch spring is provided with good lateral guidance, i.e. it is held centered in the latch slit. (The width of the latch spring is measured transversely in respect to the latch slit, i.e. approximately parallel with the latch seating pin).
Adjoining the area of the latch seating, the latch spring has sections of preferably reduced width. Because of this, a large portion of the cross section of the latch slits on both sides of the latch seating device is kept open for the passage of fluff or other dirt particles. The narrower section of the latch spring preferably extends from the latch seating device as far as the spring seating.
The linear dimensions of the wider section of the latch spring, which is arranged approximately in the center of the latch seating device, are preferably such that no narrower spring section can come into contact with the latch shank end. This means that the entire area or section of the latch spring which can come into contact with the latch takes up nearly the entire slit width. Because of this, latch wear and possibly also spring wear, as well as a tilt tendency of the latch spring, is on the one hand minimized, while on the other hand as free as possible a passage for fluff, rubbed-off particles and dust through the latch slit and past the latch spring is assured.
In a preferred embodiment, the width of the latch spring in the section of reduced width is less than half the width of the slit. It preferably is less than a third of the slit width. By means of this a particularly free passage is achieved.
Regarding its longitudinal axis, the latch spring is preferably designed to be symmetrical. In this case the narrower section of the latch spring is constituted by two recesses provided on both flanks of the latch spring. Such a spring has a particularly reduced tendency to tilt. However, it is also possible to design the latch spring asymmetrically. In this case the latch spring can have a recess on only one side. The recesses ahead of and behind the latch seating device can in this case be provided on different sides of the latch spring in order to make the forces on the spring symmetrical. This embodiment incorporates the advantage of particularly wide and free dirt or fluff passages.